P1044: REAL-WORLD RUXOLITINIB TREATMENT PATTERN IN MYELOFIBROSIS PATIENTS WITH THROMBOCYTOPENIA
Authors: J. Mei, Y. Wang, S. Kabir, N. Ichikawa, S. Iino, C. Lebedinsky
Journal: HemaSphere (2022)

Background: Ruxolitinib (RUX) is the standard treatment for patients (pts) with myelofibrosis (MF) to reduce splenomegaly and improve MF-associated symptoms. RUX treatment is titrated based on platelet counts and is associated with high rates of cytopenia effect. The incidence of moderate thrombocytopenia (platelet count <100 x 109/L) is about 25% in newly diagnosed MF pts; however, the prevalence is about 67% in all MF pts. Low platelet count has been identified as an important surrogate marker of survival in MF pts with associated poor clinical features. Thrombocytopenia is also an independent predictor in the Dynamic International Prognostic Scoring System plus (DIPPS plus), with an actual 1.4-fold increased risk of death. Thus, treatment of MF pts with thrombocytopenia confers a unique challenge and unmet medical need. Real world studies will provide a perspective on the current management of MF pts with thrombocytopenia. Aims: To characterize the disease and RUX treatment pattern in MF pts with thrombocytopenia using de-identified insurance claims data in the US. Methods: The IBM MarketScan® Medicare Supplemental Database data was retrospectively analyzed to identify pts aged ≥18 years with ≥1 claim for RUX and ≥2 non-diagnostic medical claims for MF (ICD-10 D47.4, D7581) from 2017–2019. The first RUX claim on or after the first MF claim defined the index date. Pts who continuously enrolled in a health plan for 3 months before the index date and 6 months after the index date were included. Clinical characteristics and RUX treatments were compared in MF pts with or without a history of thrombocytopenia prior to RUX initiation. Results: The database contained 136 MF pts who had received treatment with RUX. Median age was 61 years, 61% were male, 62% of pts had primary MF, and 38% had post-polycythemia vera or essential thrombocythemia MF. Prior to initial RUX treatment, 57% of pts had a diagnosis of splenomegaly, 56% had anemia, 25% had thrombocytopenia, 19% had received RBC transfusion, and 7% had neutropenia. During RUX treatment, 25% of pts had a new diagnosis of thrombocytopenia, 22% had neutropenia, and 19% had anemia. Pts with a history of thrombocytopenia also had more anemia (79% vs 48%, p=0.001) and more RBC transfusions (44% vs 11%, p<0.001) than those without a history of thrombocytopenia. History of thrombocytopenia was associated with a lower starting dose of RUX (average starting daily dose 20 mg vs 27 mg, p=0.005), whereas history of anemia, leukocytosis, neutropenia, MF type, and splenomegaly were found to have no difference in the RUX starting dose. In addition, MF pts with history of thrombocytopenia continued RUX treatment at lower doses compared with those without a history of thrombocytopenia. During RUX treatment, 57% of pts with history of thrombocytopenia experienced anemia compared with 42% in pts without history of thrombocytopenia (OR 1.88, p=0.43). Summary/Conclusion: In this real-world data analysis, history of thrombocytopenia was a major factor influencing the RUX dose for treatment of MF pts, consistent with prescribing data that RUX dose is adjusted based on platelet counts. These data show that pts with thrombocytopenia were treated with lower doses of RUX in clinical practice. Additionally, history of thrombocytopenia was associated with history of anemia; thus, these MF pts may be more prone to develop anemia during RUX treatment compared with pts without a history of thrombocytopenia. Our findings underscore the need for more treatment options to manage MF pts with thrombocytopenia. *Equal contribution.